between two lungs
by bravevulnerability
Summary: "Breathe, Castle," she instructs, calm despite the erratic beat of her heart. "Just breathe for me." Based on a tumblr prompt.


**A/N**: Set during 3XK (3x06)

Based on a tumblr prompt: _3XK strangles Castle to unconsciousness before escaping the motel. When Beckett breaks down the door she believes he's dead for a brief moment._

* * *

When she breaks down the door, she calls for him. There's no answer and she feels her tongue go heavy like a dead weight in her mouth, making the process of breathing hard and stuttered. Her flashlight illuminates the dark room, but it falls to the ground after landing on him.

"Castle," she chokes, forgetting all about procedure as she staggers to the toppled chair on the ground, the one he's tied to. Just like the rope tied around his neck.

Kate kneels at his side, continuing to call for him and continuing to receive no answer. The rope tangled around him is loose, as if it was simply left there after the strangler finished the job. It's the same kind of rope Jerry Tyson would strangle his victims with, but Castle cannot be dead like those women. God, if he's…

She tosses the rope aside, sweeps her fingers over the pale skin of Castle's face, down to his neck. For a second, she can't locate a pulse, no sign of life, and she panics - chest constricting, heart tripping with terror. But she dips her fingertips into the skin beneath his jawbone one more time, just above the angry red patterns marring his throat, and closes her eyes, blocking out the horror and the chaos behind her, and concentrates on the slow, barely there thud that makes itself known for her.

Hope ignites in her chest and she lowers her mouth to Castle's, forces oxygen from her lungs to his. She's barely begun chest compressions when he gasps awake, coughing and sputtering, eyes wild with panic as they meet hers.

"Breathe, Castle," she instructs, calm despite the erratic beat of her heart. "Just breathe for me."

He complies to the best of his ability, inhaling steady and slow, just as the EMT pushes her aside. Beckett helps the paramedic right the chair Castle's still tied to and goes to work at cutting the ropes at his hands while the man quickly checks Rick's vitals and talks him through breathing techniques.

"Kate," he rasps, his voice scratchy and raw, and Beckett leans in closer, shouldering the paramedic out of the way. "Tyson. He's-"

"I know," she assures him, hands rising to cradle his face by their own accord and he relaxes into her palms. "We'll worry about it later, okay? Just - god, Castle. I couldn't find your pulse and I thought-"

The press of Castle's hands at her curved spine, willing her closer, feels all wrong in the midst of a near crime scene, his choked breaths filtering past his lips and onto her shoulder as he holds her against him, half of her standing, the rest of her hunched and curled into his chest. But she doesn't dare move away.

"Ambulance." Her voice cracks on the word and Castle's hands - one at her nape, the other at her hip - squeeze in comfort she doesn't deserve. She's not the one who nearly died. Kate turns her nose into his cheek, resting there, inhaling his aftershave, listening to his heartbeat. "You need an ambulance, Castle."

Beckett straightens and extends her hands to him, not letting go once she's hauled him from the chair. She keeps a palm at his back on the walk out of the room, down to the ambulance stationed in the parking lot, and she remains with him as the same paramedic who checked him over only minutes before examines the marks at his neck, the indentions of the ropes that cut into his delicate skin.

Castle's gaze remains locked on her face and each time he flinches at the light touches to his neck, she squeezes the fingers laced with hers in her lap.

"He's free to go. He'll have a sore throat for a few days, as well as some bruising, trouble swallowing, but I don't see any permanent damage. Aside from the discomfort, he should heal without issue," the older man says, kind and sympathetic as he looks from Rick to Kate. "But for now, I would keep an eye on him, especially when he's at rest, to make sure his breathing remains consistent."

Kate nods without a moment of hesitation, even as Castle looks to her with an arched eyebrow, but she doesn't waver in the decision he isn't even aware she's made. She'll voluntarily stand sentinel at his bedside for every night until all evidence of this injury disappears if she has to.

* * *

In her cruiser, he struggles with the seatbelt, anxiety filling his eyes at the safety belt sitting so close to his neck, and it strikes her that this is going to affect him long after the necklace of red and purple has faded from the skin of his throat. And it makes her want to find Tyson herself, force him to pay for laying a hand on the man beside her.

She keeps her fingers splayed on his knee throughout the drive to his loft, circling her thumb over his patella every time the strain of his breathing grows short and unsteady, and by the time they arrive at his home, he doesn't look much better, but his focus is back on her, not on the seatbelt.

"You don't have to stay," he croaks once they're both standing on the sidewalk outside his lobby.

She had always thought that if the opportunity ever presented itself, Castle would jump at the chance for her to take care of him. She had pictured him playing up his ailment, needling her with nurse jokes. But now, as he stares at his shoes and winces through a rough swallow, she realizes he resembles her in more ways than she ever would have imagined.

He would rather suffer alone.

Kate catches his elbow, curls her fingers around the bone before allowing them to trickle down the inside of his arm, down to his hand, where her palm meets his for a kiss and her fingers entangle themselves with his. He looks over at her, eyes dark blue - so entrenched with so many different forms of agony - and attempts a smile that hardly curves his lips.

"I want to be here," she murmurs, tugging him forward. He doesn't question her any further, only follows her into his building, straight to the elevator, and up to his loft. She doesn't let go of his hand, even after they're safely locked inside his home.

"Do you want me to get your mom?" she asks as they enter the dimmed foyer. She spies a note on the island in the kitchen, guessing it's from one of the women upstairs, but Castle shakes his head.

"It's late," he mumbles. "I'll discuss it with them tomorrow."

He takes the lead, guiding them through the living room, into his office, and finally the bedroom. Nerves - totally inappropriate, misplaced, irrational nerves - rattle around in the pit of her stomach as she crosses the threshold with him. She just… well, she never imagined her first time in his bedroom going quite like this. Not that she had imagined it going other ways…

"Did you want to use the shower?" he asks in a whisper, all he'll be able to manage tonight, and she shakes her head.

"No, just a spare toothbrush if you have one. And maybe some clothes to sleep in?"

He shuffles past her and rummages through the middle drawer of his dresser, retrieving a large t-shirt and a pair of boxers, holding them up to her for approval.

She takes the black v-neck with a smile, the boxers with a light blush.

He gives her the time to change before joining her in the bathroom, the hard cobalt of his eyes softening to swirling cerulean at the sight of her in his clothes. But he's still wearing his dress shirt when he enters the room, the upper half of his pajamas still clenched in his hands, apprehension hiding in the frown lines that sit like parenthesis around his lips as he stares down at the t-shirt. He doesn't expect her help, she knows she isn't meant to see the uncertainty that comes with the simple act of tugging a shirt over his head, but she does, and she steps into his space, curls her fingers around the first button of his dress shirt.

"Kate."

She ignores the grizzly rasp of her name and trails her fingers from his chest to his waist, unfastening each little white disc of the powder blue shirt that once made his eyes shine. She pushes the material from his shoulders, eases his undershirt up his body next, stretching the neck of the material when it reaches his throat. He holds his breath as she maneuvers the shirt over his head and slips it down his arms, allowing it to drop to the tile of the bathroom floor, atop his dress shirt.

He takes a deep, shaking breath when he stands bare in front of her, broad chest and abdomen exposed, and she can't help but trail her hand up the side of his ribs, splaying her fingers over the frame of bones protecting his heart.

"Kate."

Her name is a warning this time, one she never thought she would hear from Castle.

She snatches her hand back and concentrates on the shirt she steals from his hands, on gently slipping the worn fabric over his head without grazing his injuries. When he's fully dressed again, he offers her another weak lift of his lips.

They brush their teeth side by side, oddly domestic, which would usually unsettle her, but she finds the simple act to be pleasant tonight, comforting even. She realizes she could envision them like this, under different circumstances, better circumstances. She realizes she could be happy in his clothes, in his space. With him.

Comfort crumbles under a subtle ripple of awkwardness when they meet at his bed. Castle offers her the choice of either side, but she's already picked the one less touched, the one with the empty bedside table and perfectly fluffed pillows with no signs of a recent occupant. Her mind flutters to questions about Gina and it must show on her face.

"We broke up," Castle lets out as he crawls into the bed, carefully easing into a horizontal position and propping his neck against a plethora of pillows to keep his head slightly elevated.

Kate follows, slipping under the warm, grey comforter, under the sinfully soft sheets. She remains sitting up in the bed though, smooths her hands out over the fabric patterned with geometric shapes.

"Me and Josh too," she gives back, stealing a sideways glance and seeing the first real hint of a smile for the first time tonight. She can't help but smile back and inch closer in the bed, eradicating the arm's length of space between them. "Will you be able to sleep?" she murmurs, reaching out with tentative fingers and brushing them over the path of swollen skin. He doesn't flinch at her touch, only watches her with curiosity as she traces the line of his injury.

"Maybe," he mumbles, capturing her wrist, holding her hand to his sternum. "Will you?"

"I have to watch you," she protests, but he gives her a reproachful look.

"You also have to sleep, Beckett. Besides, wasn't it you who said the whole staring thing is creepy?"

A grin twists at her mouth and she lifts the hand from his chest, uses it to cup his jaw, swipe her thumb over his upturned lips. But at the look of wonder her actions provoke, she quickly draws her hand back, curls it into her chest and diverts her eyes. The sudden need to touch him is unnerving. They don't _do _touching.

"I have an idea," he rasps, but his eyes are twinkling as he extends an arm to her, waiting patiently for her reluctant figure to move into his side before curling his arm around her shoulders, coaxing her to lie down, her head to his chest. Apparently, all lines and boundaries have been erased, blurred and wiped away by the events of the last couple of hours, because they're definitely doing the touching thing now. "There, now you can just listen to my breathing. If your pillow stops moving, then feel free to panic."

She huffs and lifts on her elbows beside him, catches him smiling. She hadn't expected to see anything close to a smile tonight, not after everything he had been through, but he's looking at her like none of it matters, like it's just the two of them breaking all the unspoken rules that have always been between them. He looks happy, happy that she's here with him, momentarily taking his mind off of the excruciating pain encircling his neck, and she decides not to stop when she notices herself drifting closer. Castle's smile fades, his eyes narrowing in on her lips instead, fluttering closed when she presses a gentle kiss to his mouth.

She doesn't remain long, not wanting to risk even the slightest detriment to his breathing, but she lingers, touching her forehead to his as he sifts his fingers through her hair and cradles her skull in his large palm.

"I'm so glad you're okay," she sighs, nuzzling his cheek.

"I'm glad you insisted upon playing nurse for the night."

Kate rolls her eyes, captures one last chaste kiss just to taste the spark of electricity that comes to life when their lips touch, and returns her head to his chest

* * *

She wakes twice in the night to check on him, finding him awake the second time, attempting to maneuver out of the bed without waking her. She forces him to remain under the covers in the early dawn of the morning while she retrieves the glass of water and pain medication for him.

"Okay?" she murmurs after he takes a long sip, the cool liquid appearing as both a relief and a struggle for his abused trachea.

Castle nods and sets the glass on the nightstand. It's too early to be awake, but she can feel that neither of them intend to return to sleep.

"He's going to kill again," Rick scrapes out, the defeat in his crumbling voice making him sound even worse. "All because I couldn't stop him."

The noose around her heart tightens and she takes a seat at his side of the bed, her thigh pressing to his hip.

He glares at his hands, clenching his fists in the comforter. "I just feel so…"

She doesn't know if his sentence trails because of the precarious state of his throat or because there simply are no words to describe the torment of his emotions, the unwarranted guilt and anguish of allowing a killer to get away, but she takes his hand nonetheless, earns his gaze as well.

"I know the feeling," she says quietly, she knows it all too well and the understanding in his eyes tells her he knows it too. His fingers tighten around hers. "But you're not in this alone. I'm here," she whispers the promise to him, surrounded by the silence of his bedroom and the thin strips of sunlight slipping through the slit in the curtains. Her eyes skirt along the skin of his throat once more, noticing the swelling has gone down in the past few hours, before flickering back to his.

This is not how she had envisioned this going - them. She had sworn to herself that she wasn't ready for this, for anything with him, that she never would be. Not after the summer. But despite the hurt, the miscommunications and missed opportunities, despite the walls she know still line her ribcage like a fortress, her heart has never felt more open, more ready. And maybe the fact that he had nearly died played a role in her decision, but it doesn't change the fact that she's always felt, deep down inside, that she and Castle were inevitable in some way.

In the beginning, she had anticipated nothing more than a night of sex somewhere down the line, the chemistry between them too strong to ignore forever, but as time passed, she's learned it could never be so simple. A one night stand would never work, not with them, she would want more. She already does.

Why wait?

He brings their locked hands to rest in the middle of his sternum, her knuckles pressed up against the cage of his ribs, just over his heart.

"You sure?" he murmurs, the words broken and abraded, but soft, hopeful.

Kate smiles and reaches forward to comb her fingers through his hair, watching in gentle amusement as the motion elicits a purr of contentment.

"Yeah, Castle. I'm sure."

* * *

**A/N: Thank you to the anon who sent me this fantastic prompt, I truly wish I could have come up with something better for it. **


End file.
